Had my second PET CT SCAN.

[Parscore]

My first scan was about a year ago and was the PET CT F-18 PYLARIFY. 3 days ago, did the GILLIUM 68. Somewhat different results in the SUV uptake. Gillium gave a lesser reading on the known spots. I still have my prostate and so far, no chemo. Opinions on which PET is a more valuable reading?

[Tall_Allen]

Pylarify was better when used in the same patients.

[Parscore in reply to Tall_Allen]

Thank you. I received them at two different sites. Swedish did not have it available when I did the first scan.

[tango65]

What were the SUV values in relation to the SUV of the liver.? Lu 177 PSMA treatment is more effective if the SUV in the mets is greater than the SUV in the liver.

[Parscore in reply to tango65]

They certainly are. I will be discussing with OC in a week or so. Thanks

[Cooolone]

Have posted this a few times... The study by which the superiority proclamation of PLY over G68 are made are misrepresented... There certainly are advantages with using PLY, but it is not superior or has it been tested head to head, not to my knowledge or what I've yet come across.

See below:

The following findings emerge from this analysis:

All suspicious lesions identified with [68Ga]Ga-PSMA-HBED-CC were detected with [18F]DCFPyL consistently.

[18F]DCFPyL demonstrated a significantly higher SUVmax as compared to [68Ga]Ga-PSMA-HBED-CC in consistent lesions and a better tumor to background ratio when the kidney, spleen, or parotid was used as a reference organ. The tumor to background ratio did not differ significantly between [18F]DCFPyL and [68Ga]Ga-PSMA-HBED-CC when the liver or the mediastinum was used as a reference organ. Although based on a small number of subjects, these findings support the notion that [18F]DCFPyL provides at least comparable tumor/background contrast as observed with [68Ga]Ga-PSMA-HBED-CC.

Using [18F]DCFPyL, additional suspicious lesions plausible for further metastases were detected in 3/14 patients. This indicates a high sensitivity of this tracer.

One explanation for the higher detection rate using [18F]DCFPyL can be found in the higher injected dose, which allowed later acquisition times, potentially leading to better signal to noise ratios due to reduction of nonspecific signal. Lower background activity has been observed for the [18F]DCFPyL in some organs such as the kidney. Independently from injected dose, faster clearance of the tracer from non-target tissue and higher affinity, may potentially have contributed to the detection of additional skeletal metastases observed for [18F]DCFPyL as compared to [68Ga]Ga-PSMA-HBED-CC.

It is important to notice that the higher detection rate for PSMA-avid lymph nodes by [18F]DCFPyL was not attributed to retroperitoneal PSMA foci, where the differentiation against celiac ganglia (i.e., false-positive findings) might be a question [15].

Radiolabeling with Ga-68 is an excellent alternative for imaging centers with expertise in handling the commercially available 68Ge/68Ga radionuclide generator but without own (cost-intense) cyclotron. However, a single preparation (0.3–0.6 GBq Ga-68) may only allow scanning up to two to four patients and the output depends on the half-life of the generator. As now established at our center, a single radiolabeling procedure of [18F]DCFPyL resulted in a batch containing 6 to 7 GBq of [18F]DCFPyL. This rendered it possible to examine six patients after a single preparation with an optimal dose, which represents an advantage for centers with an own cyclotron and a production of F-18 in the daily management. Furthermore, due to the longer half-life of F-18 (110 vs. 68 min for Ga-68), it may also allow transportation to remote sites from commercial vendors.

A limitation of the current study is the lack of a consistent histological validation of [18F]DCFPyL findings. In principle, it cannot be excluded that additional lesions detected with [18F]DCFPyL may represent false-positive findings. However, particularly small PSMA-positive findings cannot be easily confirmed histologically and it is impossible to assess all lesions in patients with multiple metastases. Generally, good correspondence between [18F]DCFPyL and [68Ga]Ga-PSMA-HBED-CC findings was observed, several lesions were confirmed histopathologically, and the additional bone lesions detected with [18F]DCFPyL were verified retrospectively by CT findings suspicious for bone metastases. Thus, we believe that the high sensitivity of [18F]DCFPyL, as indicated in the current study, appears plausible. Nevertheless, the findings of the current study are to be considered preliminary and the clinical performance of [18F]DCFPyL will have to be further analyzed in the future.

Another limitation can be found in the selection of patients. We did not recruit patients for both imaging series prospectively, and the selected population cannot serve as a representative sample. Due to the selection of patients with complex clinical questions (several of them being negative in [68Ga]Ga-PSMA-HBED-CC PET/CT), it might be possible that the diagnostic accuracy of [68Ga]Ga-PSMA-HBED-CC PET/CT is underestimated.

Comparison of the two tracers has not been carried out under identical conditions, i.e., mean injected dose and start of acquisition have been higher respectively later for [18F]DCFPyL, as compared to [68Ga]Ga-PSMA-HBED-CC PET/CT. It cannot be excluded that the performance of [68Ga]Ga-PSMA-HBED-CC PET/CT would have been more similar to [18F]DCFPyL under more identical examination conditions. However, it was the aim of this study to compare the two tracers under the circumstances usually available in clinical application. Generally, lower doses and earlier acquisition periods p.i. are selected for 68Ga-labeled tracers. The time period of 1 h between injection of [68Ga]Ga-PSMA-HBED-CC and the start of PET/CT was reported by many publications [2–5].

Source:

link.springer.com/article/1...

*(Bold & Italics added by me)

Always, always, read the fine print! The "better" in scanning was because a higher amount of tracer was used. The "better" is because the PLY has a longer half life and can be manufactured at a higher volume, both creating "better" access to patients for scanning. But G68-PSM-PET is still the measure they compare all the others to, so what does that tell you? Don't get me wrong, there are even better contrasting agents being tested today. But let us see the efficacy head to head shall we? That said, You won't go wrong with either being used!

Best Regards

[Parscore in reply to Cooolone]

Thank you I am much less confused.